hey and welcome to the forum.
where you registry for avast 4.8 or the new avast 5 if you where for the 4.8 it should be in your email account after a few minutes like hotmail or gmail or yahoo mail. could you have write the wrong mail address? if you are using the new avast 5 you could simple go under maintenances> registry and registry directly in the program for 14 mount of licence.
hopes this help you if not write back.